[Documentation] Update IBM Cloud CLI instructions in /etc/converter/train-deploy-wml.md

[ptitzler]

Some CLI-specific instructions in this document are based on older versions of the command line. They should be updated to reflect the latest release, which uses ibmcloud instead of bx as the binary.

Examples:

• Prerequistes section:

Current:

bx plugin repo-add Bluemix https://plugins.ng.bluemix.net
bx plugin install machine-learning -r bluemix
bx target -o ORG -s SPACE

Simpler version: (no need to add the repo - it's the default; no target required because WML service is now resource managed)

ibmcloud plugin install  machine-learning

• section 1.1

Current:

bx cf create-service pm-20 lite watson-machine-learning
bx cf create-service-key watson-machine-learning WML-Key

New:

ibmcloud resource service-instance-create watson-machine-learning pm-20 lite us-south
ibmcloud resource service-key-create WML-Key Writer --instance-name watson-machine-learning

• section 1.2

ibmcloud resource service-key WML-Key

Here on it should only be necessary to replace bx with ibmcloud
...

There's a good chance that other documentation is impacted as well. This is the first doc I've tried to follow.